Serendipita indica is a beneficial plant-fungal endophyte which colonizes a wide range of agriculturally important crop plants e.g. barley (Hordeum vulgare). The beneficial effects of Serendipita indica rely on their successful colonization of root apoplastic space of their host plants. Previously, FGB1:FITC488, a lectin-based probe was successfully employed to monitor the root colonization process mediated by S. indica. In this study, our lab discovered a carbohydrate-based structure called the polysaccharide matrix (PM) produced by the fungus in the root apoplast. The polysaccharide matrix is not only produced by Serendipita indica but is also prevalent in several plant beneficial and pathogenic microbes such as Bipolaris sorokiniana. Carbohydrate metabolic process (CMP) mediated by carbohydrate-active enzymes (CAZymes) in apoplast play a major role in plant-microbe interactions. Although extensive studies have been performed on the CMP associated with microbial structural cell wall polymers such as chitin and peptidoglycan, the CMP associated with the fungal-derived polysaccharide matrix had not been studied up to now during bipartite or multipartite plant-microbe interactions. 

Balakumaran aimed to address these outstanding questions:

1. What is the composition and structure of the polysaccharide matrix produced by S. indica and other plant-associated microbes? (Glycomics and proteomics)
2. What are the functional roles of PM during bipartite and multipartite interactions?
3. Do plant apoplastic cazymes target the polysaccharide matrix to generate novel bioactive components important for signaling? (Carbohydrate analytics and activity assays)
4. In the context of multipartite interactions, does the polysaccharide matrix serve as a nutritional source for other beneficial plant microbiota?
5. How is the polysaccharide matrix recognized and utilized by the beneficial microbes? (Gene cluster identification and metabolic flux analysis)